This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2001-381555, filed Dec. 14, 2001; and No. 2002-299117, filed Oct. 11, 2002, the entire contents of both of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a vehicle roof mount antenna.
2. Description of the Related Art
FIG. 1 show an example of a concrete structure of a swiveling pivotal mount portion of a general retractable type vehicle roof mount antenna 10 in particular. Reference numeral 11 denotes an antenna rod, and 12 designates an antenna base used to attach the antenna rod 11. A joint assembly 13 which is attached to the antenna base 12 is provided at the lower end of the antenna rod 11.
This joint assembly 13 consists of a cylindrical member with a bottom in an axial direction orthogonal to an axial direction of the antenna rod 11. As shown in FIG. 2, a pair of hemispheric convex portions 131, 131 distanced from each other at 180xc2x0 with a central position therebetween are formed on the inner surface of the bottom of the cylindrical member with the bottom of the joint assembly 13. These convex portions 131, 131 are formed in order to give a feeling of clicking to swiveling of the antenna rod. An outer surface of the bottom of the cylindrical member with the bottom functions as a terminal portion (not shown) used to propagate an antenna signal obtained by the antenna rod 11.
Further, in order to mount the joint assembly 13 on a pivot to allow swiveling, a pair of pivotal support portions 12a, 12b are formed so as to confront the upper part of the antenna base 12. A circular hole 121 having a confronting direction as an axial direction is formed to one pivotal support portion 12a. A terminal portion 122 which is brought into contact with and electrically connected to the terminal portion of the joint assembly 13 is formed on the inner surface of the other pivotal support portion 12b opposed to the circular hole 121.
With the joint assembly 13 being positioned between the pivotal support portions 12a and 12b with an O ring 23 interposed between the terminal portion of the joint assembly 13 and the terminal portion 122 of the pivotal support portion 12b, a click cylinder 14 is inserted from the circular hole 121 of the pivotal support portion 12a through an opening of the cylindrical member with the bottom of the joint assembly 13.
This click cylinder 14 has a plate 14a embedded on the outer surface side of the bottom of the cylindrical member with the bottom. This plate 14a is manufactured by, e.g., press working, and a plurality of pairs of circular holes 141, 141, corresponding to a plurality of click positions fitted to the convex portions 131, 131 are formed.
Concave and convex shapes which engage with each other are mutually formed in the vicinity of the end portion of the outer peripheral surface on the open side of the click cylinder 14 where the plate 14a is not embedded and on the inner surface of the circular hole 121 of the pivotal support portion 12a in order to suppress swiveling of the click cylinder 14 on the surface orthogonal to the axial direction of the circular hole 121.
A coil spring 15 is inserted from the open side of the click cylinder 14 through a washer 16. Further, like the click cylinder 14, a washer 17 whose swiveling action is suppressed on a surface orthogonal to the axial direction of the circular hole 121 in the circular hole 121 of the pivotal support portion 12a is inserted.
In this state, the washer 17, the coil spring 15, the washer 16, the bottom plate 14a of the click cylinder 14, and the terminal portion of the pivotal support portion 12b are pierced by a bolt 18. Then, a nut 22 is fastened from the end of the bolt 18 on the outer surface side of the pivotal support portion 12b through a corrugated washer 19, a washer 20 and a spring washer 21, thereby constituting this pivotal mount swiveling portion.
In such a structure, the convex portions 131, 131 of the joint assembly 13 are fitted to one pair of the circular holes 141, 141, . . . formed on the bottom plate 14a of the click cylinder 14 coming into contact with the convex portions 131, 131.
A click torque is generated by the elasticity of the coil spring 15 when fitting. The terminal portion of the joint assembly 13 is electrically connected by the frictional sliding with the terminal portion 122 of the pivotal support portion 12b pushed by the elasticity of the corrugated washer 19, and an antenna signal obtained by the antenna rod 11 is propagated into the antenna base 12.
FIG. 3 shows an exterior appearance of the vehicle roof mount antenna 10 having the above-described structure. A coaxial cable 24 is extended to the antenna base 12 from its lower surface. A connection plug 25 used to establish connection with a tuner of a car having the vehicle roof mount antenna 10 mounted thereon is provided at the end of the coaxial cable 24.
The antenna rod 11 has a retractable structure such that it can be fixed to the antenna base 12 in any one of three positions, e.g., 0xc2x0, 60xc2x0 and 180xc2x0. By adjusting the click torque described in connection with FIG. 1, an appropriate feeling of clicking is given so as to assuredly fix the antenna rod 11 in each position.
By mounting the vehicle roof mount antenna 10 in such a manner that a traveling direction of a car is a left direction in the drawing while taking the influence of a traveling wind into consideration, the air pressure during the regular traveling can be minimized.
In case of parallel parking and the like, the antenna rod 11 is manually fixed in the position of 0xc2x0 or 180xc2x0 in order to prevent the vehicle roof mount antenna 10 from being damaged when it physically interferes with a roof and the like.
In the structure of the above-described vehicle roof mount antenna 10, however, an attachment angle of the antenna rod 11 is held as shown in FIG. 3.
When the antenna rod 11 has interfered with a ceiling in a garage whose height is limited, for example, the antenna rod 11 is held in the retracted state in accordance with a traveling direction of a vehicle. Therefore, a driver of the car must again manually return the antenna rod 11 to the angle of 60xc2x0 indicated by a solid line in FIG. 3 after moving the vehicle out of the garage.
With respect to handling of such an antenna rod 11, if a hand hardly gets at the antenna rod 11 when a driver is particularly small, or when the attachment position of the vehicle roof mount antenna 10 is at the center of the roof, or when a position of the roof itself is high in case of a minivan type vehicle and the like, there occurs a problem that the trouble of handling the antenna is complicated and the stain on a body of the vehicle may adhere to a cloth in some cases.
In case of a minivan type vehicle which may have an air spoiler attached at the upper end of a rear door, if the antenna rod 11 is provided at the rear end of the roof, the air spoiler may interfere with the antenna rod 11 when the rear door is opened. Therefore, a vehicle manufacturer has a drawback that an attachment position of the antenna rod 11 must be restricted on the design stage.
In order to eliminate the above-described problems, there has been also considered an antenna having an electric mechanism such that the attachment angle of the antenna rod 11 can be freely variably set from the inside of a car. However, a structure of the apparatus, attachment to a car, arrangement of wirings and others are complicated, which leads to a very high cost.
It is an object of the present invention to provide a vehicle roof mount antenna which has a very simple structure but can prevent an antenna rod protruding from a vehicle from being damaged by an external force and can automatically and easily return an attachment angle to a predetermined position.
According to the present invention, there is provided a vehicle roof mount antenna comprising: an antenna rod; an antenna base which attaches the antenna rod so as to be capable of swiveling; a joint portion which is provided at one end of the antenna rod and consists of a cylindrical member in an axial direction orthogonal to an axial direction of the rod; a pair of pivotal support portions confronting the upper portion of the antenna base so as to mount the joint portion on a pivot in a swiveling manner; and a bolt and a nut which are inserted into a through hole provided to one of a pair of the pivotal support portions, pierce the joint portion and the other pivotal support portions and are fastened together; and a spring mechanism which is provided with respect to the joint portion in the antenna base and automatically restore the joint portion and the antenna rod to a predetermined swiveling position by giving its elasticity even if the swiveling position of the joint portion and the antenna rod is changed by an external force applied to the antenna rod.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.